the attention of many dairy

farmers on the advantages

of ammonia-treated whole-

crop forage – now widely

referred to as alkalage.

But even those feeding 78

D-value silage this winter

are among the new converts.

Jeremy Hunt reports

IT isnt just those dairy farmers faced with a clamp full of poor quality silage this winter who are waking-up to the potential of alkalage, says Lancs-based nutritionist Alan Sayle.

"Dairy farmers with herds in prime grass growing areas who are renowned for consistently making top quality silage, are now incorporating alkalage into their feed regime.

"Making alkalage is not just an option for those who find it difficult to make good quality grass silage. It has a wide harvesting window, bringing a valuable degree of flexibility to forage making, but the nutritional advantages of alkalage are now being recognised by high-flying grassland farmers.

"Many are realising the limitations of feeding large amounts of high D-value silage to heavy-yielding Holsteins," says Mr Sayle.

Low levels of protein and poor digestibility are also widespread in grass silages this winter, but he believes farmers who have grown and harvested alkalage are in a strong position to tackle these deficiencies more effectively.

"They have the chance to lift the energy level from say 10ME to 12.8ME. That puts them in a much needed recovery situation which will undoubtedly be beneficial in terms of winter production from forage," says Mr Sayle.

Nutritional benefits

But even those with stocks of silage up to 78 D-value are starting to experience the real nutritional benefits of incorporating alkalage into the winter feed regime.

Mr Sayle has been advising a Lancs dairy unit milking 140 cows where production has always been underpinned by the farms ability to produce top quality grass silage.

"This farm produces powerful grass silage, but after last winter the cows just fell apart after months of high forage intakes and heavy concentrate feeding. Something had to be done to counter the effects of high levels of protein energy being consumed by the cows.

"We have always been told that high D-value silage is exactly what we should be aiming to produce to most efficiently feed high yielding cows. To an extent thats true, because you need the nutrient density to get the most out of grass."

But Mr Sayle says there is a tendency to forget that the cow is a ruminant. High quality grass silage, often soft and wet, lacks the stimulation needed to achieve adequate rumination.

"And its also acidic. To preserve it we are plying this material with silage additives to produce strong concentrations of lactic acid which, in reality, is the last thing a cow wants to eat.

"Lactic acid is used as energy lower down in the alimentary tract, but its not what the rumen wants. Its a byproduct of fermentation. What we are actually doing here is trying to ferment it again.

"The cow needs energy in a form that can used by her rumen bacteria, like simple sugars and starches."

The herd owner who consulted Mr Sayle had found that although his cows had milked well on a diet of top quality silage and high levels of concentrate, all was not well by end of the winter.

"The cows were described as having fallen apart. The forage was passing through them too quickly and the herd was under severe pressure from acidosis as a direct result of the feed regime."

With the aim of providing a basal forage part of the diet that would encourage healthy rumination, and one which would enable cows to consume relatively high levels of concentrate without becoming acidic, it was decided to produce some whole-crop forage for the 1999-2000 winter. A block of 10ha (25 acres) of wheat was sown last autumn.

Herd average

"Here was a situation where a family prides itself on grassland management, is making top quality silage, has a herd average of 8000kg, and yet feels they have gone as far as they can on the present system."

This farm harvested the wheat as a whole-crop alkalage of 11.6ME in mid-August and began offering it to cows as a once-a-day feed in September.

"Yields showed an immediate lift of three litres, but the long term benefits will be seen this winter as the alkalage is incorporated into the forage part of the diet, providing structural fibre countering the acidity of the grass silage. This is high starch inclusion -about 40% – with ample structural fibre to enhance rumen function."

According to Mr Sayle, one of the problems of high-quality silage, which is often quite moist, is the high percentage of sugar used up to produce the acid needed to preserve the forage.

"Because alkalage is produced from the addition of ammonia – via treatment with an additive – and all the sugar material that was in the original crop is converted into starch in the ears, the one major ingredient we are short of in the overall diet is sugar."

Mr Sayle now favours lactose as the most cost effective sugar source, either in dry or liquid form.

"It enables the best use to be made of the alkalage but also, in this cost-conscious time for dairy farmers, presents the chance to use urea.

"A lot of farmers assume that because ammonia has been used to create the alkaline whole-crop forage, the last thing thats needed is urea. In fact a lot of high yielding herds are now using 150g of urea at 60p a unit of protein against soya at £3 or more per unit of protein.

"The use of urea in this way -something we would not have considered in the past with grass silages with low sugar levels – is indicative of the changes taking place in forage diets."

Dairy farmers who traditionally make good quality silage were hit by poor mid-May weather. The resulting silage – low D-values at around 62 and proteins down to around 12% instead of the more acceptable 14% – has once again served to highlight the dependency on a narrow window of opportunity in the grass growing season upon which the profitability of winter milk production depends.

Different approach

"We should be looking at these silages in a different way. Not saying that 62% of the forage is digestible, but that 38% is indigestible.

Mr Sayle says that farmers who have sown a crop of wheat are in a fortunate position.

"Alkalage provides the chance to recover the situation created by poor quality silage by making a forage at 70% dry matter – three times more than grass silage, 75 D-value and 40% starch, costing about £34/t.

"That high dry matter means a cow only has to take one mouthful of alkalage to achieve the same dry matter intake that would demand three mouthfuls of silage." &#42